feat(notify): 重构通信内核并补齐 stream/bulk/record/transfer 能力

- 引入 LogicalConn/TransportConn 分层，ClientConn 保留兼容适配层
  - 新增 Stream、Bulk、RecordStream 三条数据面能力及对应控制路径
  - 完成 transfer/file 传输内核与状态快照、诊断能力
  - 补齐 reconnect、inbound dispatcher、modern psk 等基础模块
  - 增加大规模回归、并发与基准测试覆盖
  - 更新依赖库

file_event_metrics_test.go

@@ -0,0 +1,33 @@
+package notify
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFillFileEventTimeline(t *testing.T) {
+	event := FileEvent{
+		Received: 150,
+	}
+	timeline := fileEventTimeline{
+		startedAt:         time.Unix(100, 0),
+		updatedAt:         time.Unix(110, 0),
+		previousUpdatedAt: time.Unix(106, 0),
+		previousProgress:  90,
+	}
+
+	fillFileEventTimeline(&event, timeline)
+
+	if got, want := event.StartedAt, timeline.startedAt; !got.Equal(want) {
+		t.Fatalf("startedAt mismatch: got %v want %v", got, want)
+	}
+	if got, want := event.UpdatedAt, timeline.updatedAt; !got.Equal(want) {
+		t.Fatalf("updatedAt mismatch: got %v want %v", got, want)
+	}
+	if got, want := event.StepDuration, 4*time.Second; got != want {
+		t.Fatalf("step duration mismatch: got %v want %v", got, want)
+	}
+	if got, want := event.InstantRateBPS, 15.0; got != want {
+		t.Fatalf("instant rate mismatch: got %v want %v", got, want)
+	}
+}